The present invention relates to a coded anti-theft system, particularly to a coded anti-theft system composed of relays and timers.
The coded anti-theft system commercialized at the present time usually utilizes an electrical integrated circuit which has the following drawbacks.
(1) The conventional anti-theft system dissipates power after being actuated, that is, the control circuit being actuated will further use power to maintain a conductive status, thereby sustaining an alert mode. Since staying in the alert mode requires the dissipation of a relatively high amount of power, the conventional anti-theft system is apt to cause an insufficient amount of power which disables the function of the coded anti-theft system.
(2) The conventional anti-theft system requires a memory device to store the code, which requires power to maintain. Therefore, when the power is insufficient, the memory device will lose the code and the user has to set a new code.
(3) The function of integrated circuit in the conventional anti-theft system is easily affected by the peripheral temperature, especially when the frequency of the integrated circuit drifts when the anti-theft system is used in a relatively high-temperature environment. Although the anti-theft system is installed with a temperature compensation circuit, the installation cost is higher and requires more maintanance.
(4) The electrical anti-theft system is easily interrupted by peripheral electronic waves, causing errors in the function thereof. A remote control anti-theft system used at the present time has merely a narrow band of frequency, and a number of signals have to be transmitted in the limited amount of channels. This easily causes interruption between two signals which are in the same channel. In addition, more and more decoding devices have been commercialized, which are able to decode the code of the remote control anti-theft system.
(5) Most anti-theft systems are easily interrupted by shaking and noise, because they are motion-activated or sound-sensing types of remote control anti-theft systems. These types of anti-systems are apt to experience errors in function due to environmental elements. Although the sensing device implemented in this anti-system is adjustable, if the sensitivity of the sensing device is adjusted too high, the anti-system may have erroneous response even by some non-aggressive stimulus, such as a car moving nearby, and if the sensitivity is adjusted too low, the anti-theft system may not detect aggressive activity.
The inventor of the present invention has created a coded anti-theft system which utilizes a combination of relays and timers to prevent the above drawbacks of conventional coded anti-theft systems.